Clean-up the README file.

README

@@ -13,10 +13,9 @@
 
    XRootD is supported on the following platforms:
 
-  * RedHat Enterprise Linux 5 and 6 and derivatives (Scientific Linux)
+  * RedHat Enterprise Linux 7 or greater and their derivatives (Scientific Linux)
     compiled with gcc
-  * Solaris 10 compiled with SunCC
-  * MacOSX 10.6 and 10.7 compiled with gcc or clang
+  * MacOSX 10.6 or greater compiled with gcc or clang
 
 2. B U I L D   I N S T R U C T I O N S
 
@@ -30,8 +29,8 @@
 2.1 Build system
 
   XRootD uses CMake to handle the build process. It should build fine with
-cmake 2.6, however, on some platforms, this version of cmake has problems
-handling the perl libraries, therefore version 2.8 or newer is recommended.
+cmake 3.6 or greater. It may be also possible to use version 2.8 but this
+is neither recommended nor supported.
 
 2.2 Build parameters
 
@@ -83,9 +82,4 @@ handling the perl libraries, therefore version 2.8 or newer is recommended.
     make install
 
 3. P L A T F O R M   N O T E S
-
-3.1 Solaris
-
-  * On Solaris x86 the Sun Studio <= 12.1 compiler optimization algorithms
-    are broken, only Debug build is supported. For the optimized mode upgrade
-    the compiler to 12.2 or later.
+  * None.